1. Technical Field
The present invention relates to a liquid ejecting head that ejects a liquid from a nozzle opening, a liquid ejecting apparatus, a piezoelectric element, and an ultrasonic sensor.
2. Related Art
A liquid ejecting head that ejects droplets from a nozzle that communicates with a pressure generating chamber by causing pressure changes on the liquid in the pressure generating chamber by causing a piezoelectric element (actuator) to be deformed is known in the related art. A representative example thereof is an ink jet recording head that ejects ink droplets as the droplet.
The ink jet recording head, for example, includes a piezoelectric element on one surface side of a flow channel-forming substrate in which a pressure generating chamber that communicates with a nozzle is provided, and causes ink droplets to be ejected from the nozzle by causing a pressure change in the pressure generating chamber by deforming a diaphragm through the driving of the piezoelectric element.
Here, the piezoelectric element is configured to have a first electrode, a piezoelectric layer and a second electrode formed on a diaphragm, and the piezoelectric layer, for example, has a problem of being prone to damage caused by moisture or the like in the external environment. In order to solve this problem, a configuration in which the second electrode covers the outer peripheral surface of the piezoelectric layer may be used. More specifically, there are piezoelectric elements in which a separate electrode is provided as a first electrode for each pressure generating chamber, and common electrode is continuously provided as a second electrode across a plurality of pressure generating chambers, and the outer peripheral surface of the piezoelectric layer is covered by the second electrode (for example, refer to JP-A-2009-172878 and JP-A-2009-196329).
However, when the piezoelectric element is driven, a problem arises in that there is concern of stress concentrating in the piezoelectric element on the end portion of a space such as the pressure generating chamber and damage, such as cracking, occurring in the piezoelectric element.
Such a problem arises not only in an ink jet recording head, but also similarly arises in any liquid ejecting head. In addition, such a problem arises not only in a piezoelectric element mounted to a liquid ejecting head, but similarly arises in piezoelectric elements used in ultrasonic sensors, and similarly arises in piezoelectric elements used in other devices other than liquid ejecting heads and ultrasonic sensors.